Do you have any information on how regularly participants checked their weight prior to enrolling in the program? Since it’s unlikely that only the males had old and unreliable home scales :), I wonder if the women just cared to measure themselves more often than men. Or perhaps women tend to be more sensitive to every fraction of a pound lost/gained.
In general, my hunch is they knowingly exaggerate (possibility #3). It leads to a sense of accomplishment, whether it’s real or not.